Continuous film processing machine



Aug. 8, 1933. J. CR ABTREE CONTINUOUS FILM PROCESSING MACHINE 1931 3Sheets-Sheet 1 Filed May 21 0:4 A6 20 2.4 LOG RELATIVE EXPOSURE FIG: 3

FIG. 2

018 1'2 lb 20 24 LOG RELATIVE EXPOSURE \CGEWQ 2 0 1 0 0 0 0.4 0'8 12 [a20 1.0a RELATIVE EXPOSURE D/RECT/ON THRU DEVELOPER LOG RELATIVE EXPOSUREF/GS INVENTOR J. CRABT REE By r\( )-Lu,\0(*.

AT T OPNE Y Aug. 8, 1933.

J. CRAB [REE CONTINUOUS FILM PROCESSING MACHINE 195 1 z Sheets-Sheet 2Filed May 21 FIG. 6

fi-Qr lNVENTO/P J. CRAB TREE LLM ATTORNEY 1933- J. CRABTREE 04CONTINUOUS FILM PROCESSING MACHINE Filed 'May 21, 1931 s Sheets-Sheet 3I /NVENTO/P J. CRABTREE ATTORNEY Patented Aug. 8, 1933 PATENT OFFICECONTINUOUS FILM PROCESSING MACHINE James Crabtree, Chatham, N. 1.,assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y.,a Corporation of New York Application May 21, 1931. Serial No: 539,047

4 Claims. (01. 95-.94)

This invention relates to photographic film processing and moreparticularly to a method and means for producing a uniform developingaction in a machine processing of photographic film.

It is the usual practice in the motion picture art to employ continuousfilm processing machines for the developing, fixing, washing and dryingof exposed photographic film which has been used to record eitherpicture or sound, or both picture and sound. The processing machinesreferred to are well known in the art and the two types in general useare the vertical tank type and the horizontal tank or tray typemachines. In both of these machines the length of exposed film iscontinuously drawn through the successive baths constituting thecomplete process.

It has been found, particularly in the development of sound film, thatthe development of the photographic sound record is not uniform for allequally exposed adjacent portions of the record. Adjacent portions ofthe sound record which should be of equal density have been found, afterdevelopment, to be of unequal density. This nonuniform developing actionproduces an undesired distortion in the wave shape of the recordedsound. Y

It is the object of this invention to produce a uniform developingaction in film processing machines.

Another object of the invention is to provide means suitable for use instandard film processing machines to eliminate the efiects producingnon-uniform developing action. a

A feature of theinvention lies in the provision of a plurality ofbrushes or squeegee units equally spaced along the path of travel of thefilm in the developing tank and adjacent the emulsion side thereof.

Applicant has discovered that the non-uniform developing action inprocessing machines arises from the following facts. The film in itstravel through the developing solution in one direction produces,relative to the motion of the film, a

' of directional ect on a recorded sound wave.

the next adjacent area and exercise a restraining influence upon itwhich results in the production of an abnormally low density in thisarea. This action may be cumulative and therefore may cause a greaterdefect in the development of the next succeedingv area.

In accordance with the method produced by this invention for insuringuniform developing action, the developer employed in developing a smallarea of the film together with the resulting products of reaction areimmediately removed from the region of the film and displaced by a freshdeveloping solution to afiect the next succeeding area of the film. Themeans provided by this invention for eil'ecting'displacement of theexhausted developer comprises a plurality of wiping units, which maytake the form of rubber Squeegees, spaced at intervals in the developingtank along the path of travel of the film adjacent the emulsion sidethereof. These wiping units are preferably set at an angle to thedirection of travel of the film.

Fig. 1 is a showing of two characteristic Hurter and Driflield curvesplotted from readings obtained from two identical sensitometer exposureswhich were subjected to identical development on a continuous filmprocessing machine.

Fig. 2 is a similar set of curves obtained from a pair of sensitometerexposures which were run through a non-circulating developer solution.

Fig. 3 shows a set of H and D curves obtained from a pair of identicalsensitometer exposm'es which were run through a circulating developersolution.

In Fig. 4 is shown a curve disclosing the results of directional effecton the development of a photographic sound record in a continuousprocessing machine.

Fig.5isa ticshowingoftheresults Fig. 10 is a'detail showing of therelative posiof film propulsion.

tions of the squeegee units and the film in either of the type machinesdisclosed.

To provide for precise control of development operation, it is customaryin the development of continuous film to attach to each length of filmthat passes through the processing machine a short length of film uponwhich a sensitometer exposure has been impressed. As is well known inthe art, this sensitometer exposure consists of a series of exposures inwhich small areas of the film are exposed to different and knownquantities of illumination. After exposure and development of the film,the measurement of the different densities produced on these areasenables one to determine the characteristics of the film materialemployed and also to measure the degree of development that has beengiven to the film.

Diificulties have been experienced in obtaining close sensitometriccontrol of the development of a continuous film in machines as describedabove. It has been found that characteristic curves obtained fromseparate sensitometric strips having identical exposures on the same orsimilar film and which were given identical development were found tovary widely. Applicant has discovered that these characteristic curvescould be divided into two distinct classes, according to the directionin which test strips are passed through the developer.

In Fig. 1 are shown two characteristic H and D curves A and B. Thesecurves were obtained from two identical sensitometric exposures whichwere given identical degrees of development. The differences in theshape of these two curves may be explained more fully by reference toFig. 10 in which numeral 1 denotes a sensitometer strip in which theareas of higher exposure precede the areas of lesser exposure withrespect to the direction of film propulsion, while 2 denotes asensitometer exposure strip in which the areas of lesser exposureprecede the areas of higher exposure with respect to the direction Thecurve A in Fig. 1 is representative of a characteristic curve obtainedfrom a reading of the developed sensitometer exposure strip 1, whilecurve B is representative of a characteristic curve obtained fromareading of the developed sensitometer exposure strip 2. It will be seenthat in curve A, in which the areas of higher density precede the areasof lower density, the areas of higher density have re-- ceived fulldevelopment while the areas of lesser density have received a lowereddevelopment. This is caused by the fact that the developer solution indeveloping the area of higher density has released products of reactionat the developed surface which make contact with the next succeedingarea to cause imperfect development of this area. In curve B, in whichthe lighter areas preceded the darker areas, the lower densitiesreceived substantially full development while the higher densities werelowered due to the action of the accumulated products of reaction fromthe lower density areas. It can therefore be seen that the extent ofdevelopment of a sensitometer exposure strip depends upon the directionin which it is sent through the developer solution.- This efiect is whatapplicant terms directional effect in the development of photographicfilm in continuous film I processing machines.

The general effect is to straighten out the shoulder in curve A and tosuppress it somewhat in curve B. As can be seen, the eiIect on theresultant gamma or slope of the curve is slight but there is anappreciable difference in the estimate of latitude (straight lineportion) and inertia (intercept on log E axis) in the two cases.

It has further been found that the general circulation of a developersolution by the pumps had but little effect in breaking up thisdirectional eifect". In Fig. 2 the curves A and B were obtained fromreadings of a sensitometer exposure strip run through the developer inopposite directions, the developer being non-circulating or stagnant.The curves obtained in Fig. 3 were plotted from readings taken fromsensitometer exposure strips as in Fig. 2 with the exception that thedeveloper solution was caused to circulate by pumps provided for thispurpose. It can be seen by reference to the two figures that adirectional efiect is present regardless of the circulation of thedeveloper solution in the developing tank of the continuous processingmachine.

Fig. 5 is a diagrammatic showing of a crosssection of the emulsion of aphotographic film on which a single frequency record had been recorded.In this figure is shown the efiect of directional efi'ect in thedevelopment of a sound record in a continuous film sound processingmachine. The film bearing the sound rec- 0rd is being propelled throughthe developer in a direction indicated by the arrow, and the second halfof the wave is subjected to the restraining influence of the product ofreaction set free in the development of the first half of the wave. Itis seen therefore that the first half of the wave will receive fulldevelopment and the second half will receive a lowered development asindicated by the difierence between .the full and dotted lines shown inthe figure. As a frequency cycle of a variable density sound recordconsists of a series of gradations of density arranged much like a pairof minute sensitometers with their high densities abutting, the readingsfor the curves shown in Fig. 4 were taken from exposures from a verysmall step sensitometer strip having steps arranged so as to give aseries of densities simulating a sound wave of 45 cycles. These curvesshow a definite difference of slope for the two sides of A-B and B-C ofthe wave as shown. It can be seen that the side of the wave leadingthrough the developer was given full development while the half of thewave following received lowered development. From the results obtainedin plotting the curves as shown in Fig. 4, it was concluded that"directional effect in a processing machine will distort the recordedsound Waves as shown diagrammatically in Fig. 5.

To eliminate directional eiTect in developing film in a continuous filmprocessing machine, applicant has produced a method and means ofeffecting uniform developing action and therefore prevent distortion inthe recorded sound wave.

In Fig. 6 is shown a continuous film processing machine 5 of thehorizontal tray type having a developing tank 6 and a fixing tank '7employed for the continuous processing of photographic film. Aphotographic film 8 is fed from a film reel 9 to rollers 10 and 11'. Twosets of rollers 12 and 13 are arranged on opposite sides of tank 6.

A driving motor 14 secured to the machine by M5 tank 6.

down to the fixing tank '7. From this tank it is led to a washing anddrying tank to complete the processing operation.

In accordance with the method produced by applicant for eliminatingdirectional effects in such machines, the products of reaction at thedeveloped surface areremoved simultaneously'at a plurality of points.This is accomplished by the provision of a number of squeegee units 21secured to the tank 6. A set of these units is disposed diagonallyacross the top and another set disposed diagonally across the bottom ofthe As shown more clearly in Fig. 10, each unit consists of a member 23having a groove therein into which is secured a strip member 24 ofrubber or some other suitable material. These units may be spaced from3" to 6" apart and at an angle to the direction of travel of the film asshown. It is desirable, but not essential that the member 24 be inactual contact with the surface of the film. However, as shown, a smallspace may exist between the two surfaces. By means of these units eddycurrents are generated at each of these points which brings about adisplacement of the solution in contact with the film surface in thatregion. The effect obtained by the use of these units is a resultingcirculation of the products of reaction in the direction indicated byarrow 26 in Fig. '7. As these products of reaction are removed from thefilm surfaces immediately and displaced by fresh developer they do nothave an opportunity to affect the next succeeding area on the film.

Readings taken from identical sensitometer exposure strips directed tothe developer in opposite direction with respect to the film emulsion ina machine equipped with such squeegee units have resulted in identicalcharacteristic H and D curves. Therefore, if no differences in thecurves result, there can be no confusion as to the characteristics ofthe film and the degree of development given.

In Figs. 8 and 9 a continuous processing machine 30 of the vertical tanktype is shown. This machine consists of a developing tank 31 and afixing tank 32. In this case the film 8 is fed from a reel 33 to twosets of rollers 34 and 35 arranged at the top and bottom of the tank 31respectively. The film 8 is fed up and down over the rollers 34 and 35as shown in Fig. 9. The rollers 34 and 35 are rotated by means of chains36 and 37, respectively, which are actuated by some suitable drivingmeans (not shown). After development the film is fed into the fixingtank and from there to the drying tank to complete the fihn processingoperation.

The sets of squeegee units 21 are secured in a diagonal position in thetank 30 and between the two sets of driving rollers 34 and 35. Theseunits may be spaced from 3" to 6" apart in the direction of travel ofthe film. The spacing between the squeegee units and the film may beidentical to that previously described in connection with the horizontaltray type machine. Each squeegee unit produces a circulation of thedeveloper in a direction indicated by arrow 39 in Fig. 9. It willtherefore be seen that by this local circulation simultaneously at aplurality of points, the

products of reaction are immediately removed to be displaced by newdeveloper before they have an opportunity to come in contact with thesucceeding areas of the film.

The directional effect is normally somewhat less in this type machinethan in the tray type machine due to the fact that in the vertical tanktype machine gravity will assist in removal of the reaction productssince they are of higher specific gravity than the fresh developer.However, the effect has been found to be sufficiently pronounced tocause non-uniformity in develop- -ment and therefore confusion as to thecorrectness of the results obtained.

The characteristic curves obtained from identical sensitometric exposurestrips developed in a machine of the vertical tank type provided withsqueegee units as described, have been found to be uniform regardless ofthe direction in which the sensitometer strip was sent through thedeveloper.

It can therefore be seen that the provision of means as described forthe elimination of directional effect in film development in acontinuous film processing machine will produce uniformity in thedevelopment of exposure strips of sensitometric latent images and alsoeliminate distortion in the recorded sound waves resulting fromnon-uniform development.

What is claimed is:

1. The combination with the developing chamber of a continuous filmprocessing machine having means for guiding and moving a photographicfilm, of means for eliminating directional effect in the developing ofsaid film, said means comprising a plurality of wiping units secured tosaid chamber along the path of travel of said film at an angle to thelongitudinal axis thereof.

2. In a continuous film processing machine, a developing chamber, filmguide rollers in said chamber, a set of wiping units secured in adiagonal position across the top of said chamber, a second set of wipingunits secured in a diagonal position across the bottom of said chamber,and means for moving said film over said guide rollers between said setsof wiping units.

3. In a continuous film processing machine, a treating .chamber forcontaining a fluid, film guide rollers in said chamber, means for movingsaid film over said guide rollers, and means for eliminating directionaleffects in the treatment of said film, said means comprising a pluralityof fixed wiping units spaced from said film and secured to said chamberalong the path of travel of said film at an angle to the longitudinalaxis thereof. I

4. A continuous film processing machine, in combination, a treatingchamber for containing a fluid, a plurality of sets of guide rollers insaid chamber, means for moving said film back and forth over said setsof guide rollers, a plurality of fixed rubber strips spaced from theemulsion side of said film at an angle to the longitudinal axis thereof,said strips secured to said chamber along the path of travel of saidfilm between said sets of guide rollers.

JAMES CRABTREE.

